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Evolution 6.docx

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BIOL 121
Carol Pollock

Evolution 6: Sexual Selection (insert notes from previous day ) Experiment Examples to prove that females do show this choosing behavior - Long tailed widow bird has a long tail that allows it to be more desirable to the females therefore experiment was done by changing the tail lengths which resulted in showing those with the longer tails reproduced more often * Runaway traits: are far beyond what would be useful for natural selection, however they continue because the females continue to choose them = reproduction  Examples of runaway traits: plumage of birds, heavy pigmentations to attract females What about humans? Do we have the same kinds of engraved female selections? Pheromones are hormones that produce a chemical response in the opposite sex Experiment: they had males and females from universities Exp. 1 – males had to sleep in a shirt tonight and no added chemicals (no washing or deodorant) and these shirts were then exposed to females MHC – major histocampability complex – a way to measure how genetically close someone people are Result: they found the males shirts with different MHC (if they were not on the pill), those on the pill preferred those with similar MHC THEREFORE: Fertile = want someone very different genetically to have healthy offsprings Not Fertile = want someone similar so they may raise children, most like you Exp. 2 – same experiment, but this time females slept in shirts Result: all men found women not on the pill (mid reproductive cycle) THEREFORE: Though it may be subliminal, men are able to sense which women are ready to reproduce with - There is some kind of chemical attraction behind our relationships = wanting the most genetic variation Summary: characteristics of fundamental asymmetry of sex – Female fitness is limited mostly bt the ability to get resources for producing eggs and rearing young, while male fitness is limited by the ability to attract femalesEvolution 6: speciation 1. Biological spp. Concept = reproductive isolation – fossils? Asexual organisms? 2. Horphospeices spp. – looking at the various different looking physical characteristics and deciding what different/ how much changes on fossils A. Habitat isolation B. Behavioral isolation C. Temporal isolation- true in plants and animals D. Gametic isolation – something is done to protect the gametes from the “wrong” spp. Only gametes of the right species are able to get though E. Postzygotic barriers – if mating could occur but in the development proces
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